Solid state storage systems with no moving parts and allowing for random access are becoming increasingly attractive, given their inherent ruggedness and low or zero idling power requirements. One especially interesting type of memory device is based on the recently discovered resistive switching devices that have been shown to exhibit a memristive behavior. A resistive switching device can be programmed to be in an ON state with a low resistance or an OFF state with a high resistance. Such resistive switching devices can be used as non-volatile memory cells and can be fabricated in a nanoscale two-dimensional crossbar structure with a very high cell density.
One of the main challenges in developing high density memories based on crossbars of resistive switching devices is the half-select problem, in which devices that are not addressed may still draw significant current. In a crossbar array, there can be many resistive switching devices on each column or row wire. To program or read the value of a resistive switching device, a corresponding write or read voltage is applied to that device through the column and row wires of the selected device. The other switching devices connected to the same column or row wire of the selected device, however, are “half-selected” because they also experience significant voltage drops across their terminals. Those half-selected devices that are in the ON (or low resistance) state will contribute to a significant cumulative current draw. The current draw caused by those-half selected switching devices, which is parasitic in nature, not only leads to wasted power but also negatively impacts the read sensitivity in terms of the on/off current ratio used to determine the state of the selected device. Moreover, such high parasitic current can reduce the longevity of the circuit through heat dissipation, electro-migration, etc.